1. Field of the Invention
The present invention relates to a liquid crystal display and a fabricating method thereof, and more particularly, to a liquid crystal display and a fabricating method thereof that prevents short circuiting and coupling between pixel electrodes.
2. Discussion of the Related Art
Many efforts are made to study a liquid crystal display as a flat panel display having advantages of a high contrast ratio and less power consumption as well as being suitable for gray scale or moving picture display. In general, a liquid crystal display includes a thin film transistor substrate having thin film transistors and pixel electrodes formed in pixel areas defined by gate and data lines, respectively, a color filter substrate having a color filter layer and a common electrode formed thereon, and a liquid crystal material layer formed between the two substrates. The liquid crystal display displays an image by applying a voltage to the pixel and common electrodes to align the liquid crystal molecules of the liquid crystal material layer to control transmission of light. Accordingly, if a portion of the liquid crystal display has an interval between the two substrates that is not uniform, transmittance through such a portion is varied and produces uneven brightness. Hence, spacers are inserted between the two substrates to maintain an uniform interval.
A liquid crystal display and fabricating method thereof according to a related art is explained by referring to the attached drawings as follows.
FIG. 1 illustrates a layout of a liquid crystal display according to a related art, FIG. 2A illustrates a cross-sectional view along I–I′ in FIG. 1, and FIG. 2B illustrates a cross-sectional view along II–II′ in FIG. 1.
A liquid crystal display according to a related art includes a color filter substrate, a thin film transistor substrate facing the color filter substrate, and a liquid crystal layer between the two substrates. The thin film transistor substrate 11, as shown in FIG. 1, includes gate lines 17 and data lines 18 crossing each other to define a pixel area, a thin film transistor 20 arranged at an intersection between the gate and data lines 17 and 18, and a pixel electrode 22 formed to be connected to the thin film transistor 20.
A method of fabricating a liquid crystal display according to a related art is explained by referring to FIG. 2A and FIG. 2B as follows.
First, a plurality of gate lines 17 are formed on a first substrate 11 to be substantially in parallel with each other. A gate insulating layer 24 is then formed on an entire surface of the first substrate 11 covering the gate lines 17. Then, a plurality of data lines 18 are formed on the gate insulating layer 24 to be substantially in parallel with each other.
The gate insulating layer 24 is deposited by plasma chemical vapor deposition (CVD) using an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx), and the like having characteristics of adhesion to metal and withstanding pressure.
A thin film transistor is formed at each intersection between the gate and data lines 17 and 18. The thin film transistor is formed by stacking a gate electrode connected to the gate line, a semiconductor layer insulated from the gate electrode by the gate insulating layer, and source/drain electrodes on the semiconductor layer, successively.
Next, an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiOx) as a passivation layer 25 is deposited on an entire surface of the first substrate 11 covering the data lines 18. A pixel electrode 22 is then formed on the passivation layer 25 to be electrically connected to the drain electrode of the thin film transistor.
Then, a black matrix for cutting off light leakage and a common electrode for applying a voltage to a liquid crystal material layer are formed on a second substrate. To align the first and second substrates, alignment layers are formed of a polyimide (PI) based polymer on the first and second substrates. Alignment treatment is carried out on each of the alignment layers using a rubbing or light irradiating process.
Subsequently, ball spacers are positioned on the first substrate 11 to maintain a uniform interval between the first and second substrates. Next, a sealant is formed along a circumference of the second substrate to prevent liquid crystal material from leaking. Then, the first and second substrates are bonded together with the liquid crystal material formed therebetween.
There are a number of problems associated with the liquid crystal display and fabricating method according to the related art. For example, because the gate and data lines 17 and 18 are formed of metal, and the pixel electrode 22 is formed of conductive indium tin oxide (ITO), when the passivation layer 25 is formed of the inorganic material, such as SiNx or SiOx, a dielectric ratio becomes high and parasite capacitances are formed between the data line 18 and pixel electrode 22, and between the gate line 17 and pixel electrode 22 when a voltage is applied. Due to the existence of parasite capacitances, the distances between the pixel electrode 22 and the gate and data lines 17 and 18 cannot be significantly reduced. In addition, enlarging an opening ratio is limited.
Moreover, the liquid crystal display according to the related art has a problem of short circuiting between the pixel electrodes 22 during the patterning process for forming the pixel electrodes 22. Even if the intervals between the pixel electrodes 22 are increased to prevent the short circuiting, an effective area of the corresponding pixel electrode 22 is reduced, thereby decreasing the opening ratio.
Furthermore, the ball spacers according to the related art are not suitable for a large-sized liquid crystal displays because the ball spacers fail to remain fixed within a liquid crystal cell and move to form scratches on the alignment layers, thereby generating image stains.